Tamon's Piezo Drive 18-270

Some years ago I almost bought the Tamron 18-270 for use on a Canon T1i. In the end I purchased the Canon 18-200 lens in its place because I thought the Canon lens was sharper and felt smoother when it zoomed. About a year ago I gave that camera and the Canon lens to a family member when I upgraded to a Canon 7D.

I have been wondering how the new Tamron PZD lens, which I assume is completely new, compares to its predecessor. I understand that the IQ from a lens is a very subjective subject, but can anyone who has this lens (and perhaps had the previous version) tell me how well it works and how it compares with its competitors? Is it sharp? Does it delivery good colors? Is there any vignetting?